The invention relates to an electric hearing aid having a plurality of sound sources for supplying sound to a shared acoustic transmission arrangement Such hearing aids frequently contain devices in order to emphasize individual frequency ranges and in order to lower others. This is done because, for example, hearing aids are required which amplify high frequencies more than low frequencies in order to guarantee matching to a specific hearing impairment. Such so-called high pitch devices have hitherto been achieved, for example, in that they were realized with special microphones (6 dB or, respectively, 12 dB rise per octave in the frequency response) or amplifiers having highpass filter characteristics (cf., for example, the book "Horgeratetechnik" by W. Guttner, Thieme-Verlag, Stuttgart 1978, pp. 115 through 118).
The two possibilities cited above, however, have the disadvantage that the frequency response of the electroacoustic receiver remains unaltered so that, given full drive of the hearing aid, it is not the acoustical setting but, rather, the efficiency of the receiver which remains the determining factor for the frequency ranges supplied to the hearing impaired person. The loss of hearing in many hearing impaired persons, however, is so great that the hearing aid must be driven to the maximally attainable output level. Since, however, the frequency response at the maximum output level largely corresponds to the efficiency of the receiver, the frequency character of a high pitch device changes in this setting as it approaches the operating limit and becomes broadband so that the high pitch character is lost (cf. FIG. 2).
A hearing aid is known from the papers of the German Utility Model No. 17 39 043 which exhibits two or more differently designed sound sources augmenting one another in terms of their frequency ranges which influence a shared acoustic transmission arrangement which collects the sound. This arrangement, however, only results in an expansion of the frequency range in the sense of as broad as possible an acoustic frequency range transmittable without frequency response adaptation to an individual hearing loss.